• 한국해양공학회지
• /
• 제1권2호
• /
• pp.101-112
• /
• 1987

Fracture toughness characterization in the transition region is examined for heat-treated and ionnitrided Ni-Cr-Mo steel. After heat treatment for the specimens of Ni-Cr-Mo steel, organizations of specimens-specimens which are heat-treated and ion-nitrided for 4 hours at 500 .deg. C and 5 torr in 25%N/dub 2/-75%H/sub 2/mixed gas-, hardness variety, and X-ray diffraction pattern of the ion-nitriding compound layer are observed. Fracture toughenss test of unloading compliance method were conducted over the regions from room trmperature to -70.deg. C. The compound layer was consisted of r'=Fe/sub 4/N phase and ion-nitrided layer's depth was 200mm from surface. The transition regions of heat-treated and ion-nitrided specimens were about -30.deg. C and -50.deg. C, respectively. The transition region of ion-nitrided specimens is estimated less than that of heat-treated one, and this is the effect of ion-nitriding.

• 미생물학회지
• /
• 제27권3호
• /
• pp.291-296
• /
• 1989

Campylobacter jejuni was studied for its disinfection by heat-and cold-treatment and UV-irradiation. When C. jejuni was treated by heat, no viable cell was found after 10 min treatment at $55^{\circ}C$, whereas small fraction of cell population was survived after 60 min treatment at $45^{\circ}C$ and $50^{\circ}C$. When they were treated by cold temperature for 30 days, no cell was survived at -$23^{\circ}C$ but about 4 log of the cells were survived at both temperature of $4^{\circ}C$ and -$40^{\circ}C$. When the organisms were UV-irradiated, thier survival rates were proportionally varied to the distance of irradiation. The scanning electron microscopic studies of C. jejuni cells treated by the disinfecting agents revealed that shapes of thecells were deformed from spiral rod into spherical form. The heat-treated cells showed rough and damaged surface on the scanning electron micrographs. In the heat-treated cells, some proteins of high molecular weight appeared to become accumulated in the electrophoretic analysis. The DNAs extracted from the cells treated with the physical agents showed some differences in agarose gel electrophoresis, comparing those of normal cells.

• 한국세라믹학회지
• /
• 제38권7호
• /
• pp.602-607
• /
• 2001

Zirconia powder containing 3 mol% yttria (3Y-PSZ) was casted on the cast iron substrate by plasma spraying method. Coated specimens were then heat treated at 500$\^{C}$ in nitrogen plasma. Wear tests were performed on nitrogen heat treated and non heat treated samples at temperatures from 25$\^{C}$ to 600$\^{C}$. Wear results showed that the friction coefficient and the wear loss of both the treated and the non-treated samples showed maximum value at 400$\^{C}$. These results were explained by low temperature thermal degradation due to the monoclinic transformation. Nitrogen plasma treatment significantly improved the tribological performance. The effect of nitrogen heat treatment on tribological behavior was explained by the increased micro-hardness and decreased monoclinic faction.

• 열처리공학회지
• /
• 제33권2호
• /
• pp.72-79
• /
• 2020

To improve the mechanical properties of most structural materials for industrial applications, the control of microstructure is essential by heat treatment process or plastic deformation process. Since the mechanical behavior of structural materials is significantly influenced by their microstructure, it is inevitably preceded to understand the relationship between microstructure and strengthening mechanisms of materials which can be easily changed by heat treatment. In this regard, the nanoindentation test is useful technique for analyzing the influence of the localized microstructural change on small-scale mechanical behavior of various structural materials. Here, the interesting studies performed on various heat-treated materials are reviewed with focus on micromechanical properties obtained by nanoindentation, which are reported in the available literature.

• 열처리공학회지
• /
• 제5권1호
• /
• pp.23-31
• /
• 1992

It is investigated that Fe-C-N compound layer, defusion layer, and induction hardened layer produced by nitrocarburizing blend heat treatment in austenitic temperature with high frequency induction heating of mild steel specimen sprayed sursulf salt-bath. As the temperature of blend-heat treatment got increased, the thickness and hardness of compound layer and diffusion layer were increased. Compound layer(max. $35{\mu}m$), diffusion layer (max. 2.5mm) and induction hardened layer were gained in the shortest time 10 sec and in the case of $1000^{\circ}C$ total hardness depth of those was about 3.5mm. When the blend-heat treated specimen was reheated, maximum hardness of compound layer was dropped more than that of the reheated compound layer after sursulf treated, whereas hardness of diffusion layer was increased.

• 한국식품과학회지
• /
• 제31권2호
• /
• pp.375-379
• /
• 1999

식품공정에 있어서 비가열 살균기술로 개발되고 있는 고전압 펄스 전기장(PEF)을 사과주스에 적용하여 실용성 있는 비가열 처리 신선 사과주스의 개발 가능성을 검토하고자 하였다. 이를 위하여 PEF와 가열처리한 사과주스를 저장하면서 비타민 C, 색깔, 향기성분, 관능평가 등 품질특성 변화를 조사하였다. PEF 처리와 가열 처리한 사과주스의 $5^{\circ}C$ 저장중 색깔은 큰 차이가 없었으나 비타민 C 함량은 PEF처리한 사과주스가 가열처리한 사과주스에 비하여 높은 함량을 나타내었으며, 신선 주스와 거의 같은 함량을 보였다. 향기성분도 대조구에 비하여 가열처리한 사과주스는 약 70% 이상의 심한 향기성분의 손실을 나타낸 반면 PEF처리한 사과주스는 약 15%의 향기성분의 손실만을 나타내었다. 관능적 기호도도 PEF 처리한 사과주스는 신선 사과주스와 차이가 없었으나, 가열처리한 사과주스에 비하여 유의적으로 우수한 것으로 나타났다(P<0.05). PEF 처리 사과주스는 $5^{\circ}C$에서 30일간의 저장기간 동안 품질 변화가 거의 없었다.

• 한국가구학회지
• /
• 제23권2호
• /
• pp.163-168
• /
• 2012

Specimens of seven hardwood species were heat-treated at three temperature levels of 170, 190 and $210^{\circ}C$. Their FSP's were measured by the volumetric swelling method and compared with the control's. Within a species the FSP decreases as the temperature of heat treatment increases. The FSP's of the controls range from 26.1 to 29.6%, while those of the specimens heat-treated at $210^{\circ}C$ from 16.9 to 21.8%. There were no difference of basic density between the heat-treated and control specimens. The color indexes of ash and beech specimens were measured using a colorimeter. It was revealed that the temperature of heat treatment affected on the color more than the treatment time.

• Journal of the Korean Wood Science and Technology
• /
• 제37권4호
• /
• pp.330-339
• /
• 2009

본 연구에서는 삼나무 재색제어에 적합한 적정 열처리 조건을 구명하고, 열처리에 따른 다양한 재질변화를 평가하고자 하였다. 국산 삼나무에 대한 온도제어 열처리를 통하여, $170^{\circ}C$ 이상의 열처리 조건에서 심변재 사이의 재색차이가 줄어드는 경향을 확인하였으며, 이러한 경향은 처리시간이 증가함에 따라 더 크게 나타났다. 열처리재의 평형함수율이 무처리재에 비해 50% 정도 낮아 목재의 사용과정에서 나타나는 수분에 의한 성능저하 문제를 예방할 수 있을 것으로 기대되며, 열처리가 부후균에 대한 내후성 증가에도 영향하는 것으로 확인됨에 따라 친환경 방부처리 기술로써 열처리의 적용에 대한 본격적인 연구가 필요할 것으로 판단된다. 열처리재의 역학성능은 무처리재에 비해 대체로 증가하는 것으로 나타났으나, 연성이 감소함으로 인하여 충격휨흡수에너지는 크게 감소하는 결과를 보여 열처리재의 용도를 결정하는데 있어서 이러한 물성 변화가 고려되어야 할 것이다. 열처리에 의한 물성변화의 원인을 규명하기 위하여 미세구조의 변화를 관찰하였으나 특별한 차이는 나타나지 않았다. 따라서 화학성분의 변화를 분석함으로써 물성변화의 원인을 규명하는 추가적인 연구가 필요할 것으로 여겨진다.

• 해양환경안전학회지
• /
• 제22권1호
• /
• pp.138-144
• /
• 2016

티타늄은 표면에 형성되는 보호성 부동태 피막 때문에 일반부식과 해수에서 내식성이 강하지만 염산, 황산, 인산 등의 산에서는 보호성 산화물 피막이 파괴된다고 알려져 있다. 본 연구에서는 Ti에 Al 및 V등을 첨가한 ${\alpha}+{\beta}$계에 대하여 $1066^{\circ}C$와 $966^{\circ}C$에서 5시간 용체화 열처리를 실시하고, 이 시편을 $550^{\circ}C$, $600^{\circ}C$, 및 $650^{\circ}C$에서 각각 1시간, 4시간, 8시간 및 16시간 시효열처리한 후 마이크로비커스 경도를 측정하고, 이 시편을 1N $H_2SO_4$ 용액에서 전기화학적 분극법으로 부식을 계측하였으며, 분극을 마친 시편의 표면을 현미경 조직사진으로 부식상태를 검토하였다. 시험 결과 용체화열처리한 시편이 모재와 시효열처리한 시편보다 높은 내식성을 나타내며. 용체화 온도가 높고 시간이 길어질수록 내식성은 증가하였다.

• 대한치과보철학회지
• /
• 제35권4호
• /
• pp.706-718
• /
• 1997

Ceramometal crowns are common restorations in fixed prosthodontics because of their casting accuracy, the high strength properties of the metal, and the cosmetic appearance of porcelain. However, deterioration of the initial fit of the metal coping has been observed after the porcelain firing cycle. The distortion due to repeated firing makes it difficult to fit crown margin and elicits microleakage. The major causes of distortion are the residual stress that accumulate during wax-up, casting, cold work and the induced stress caused by the mismatch of porcelain-metal thermal contraction. This study examined the marginal fit changes of metal copings in relation to repeated firing and the effects of heat treatment that reduce the distortion resulted from residual stress. The marginal changes of the copings that were treated with conventional method and those treated with heat before repeated firing, were evaluated. The metal die which represented preparations of a maxillary central incisor was fabricated, and 45 wax patterns were cast with nonprecious metal alloys. The heat treatment of each group was performed as follows. Group 1(control) : Casting - Devesting - Cold work - Firing Group 2 : Casting - Heat treatment - Devesting - Cold work - Firing Group 3 : Casting - Devesting - Cold work - Reinvesting - Heat treatment - Devesting - Firing The copings were fired 3 times. After each firing, the marginal fit changes were measured with inverted metallurgical microscope at the 4 reference points located at labial, lingual, and both proximal surface. Measurements were compared, and statistically analyzed. The results were as follows ; 1. In all groups, the highest value of marginal fit changes of the copings studied were found after the first firing cycle. 2. When the distortion of each experimental group at the first firing cycle were compared, group 1 exhibited the greatest changes($20-27{\mu}m$), followed by group 2($9-13{\mu}m$), and group 3($8-10{\mu}m$). 3. The copings treated with heat before devesting(group 2) revealed significantly smaller marginal fit changes than the copings treated with conventional method(group 1). (p<0.01) 4. The copings treated with heat after reinvesting(group 3) revealed significantly smaller marginal fit changes than the copings treated with conventional method(group 1). (p<0.01) 5. No siginificant differences in marginal fit changes were found between the copings treated with heat before devesting(group 2) and the copings treated with heat after reinvesting(group 3). (p>0.01)